1. Field of the Invention
The present invention relates to a vehicle-to-vehicle communication method and apparatus, and particularly to a vehicle-to-vehicle communication method and apparatus where a vehicle in a network issues a request to which another vehicle in the network responds and, if necessary, takes action according to the request.
2. Description of the Related Art
Conventional methods for asking other drivers to do something include blowing the horn, raising a hand, nodding the head, flashing the headlights, and blowing a siren.
For example, a first driver on a secondary road who wishes to squeeze into a line of vehicles on a busy highway typically uses body language such as raising a hand and nodding the head. A second driver may operate instrument switches such as flashing the headlights to permit the first driver to squeeze in front of the second driver. Unfortunately, making a request to squeeze in front of another vehicle by raising a hand is not always successful because the driver expected to respond to the request may not notice the raised hand. Obviously, this method of raising a hand does not work in an alley with walls on both sides. Furthermore, a first driver who wishes to squeeze in front of a second driver on a busy highway may cause a collision with the vehicle of the second driver; this collision may occur if the first driver mistakenly thinks the second driver permitted the first driver to squeeze in front.
Japanese Unexamined Patent Application Publication No. 11-170887 discloses a method for avoiding a collision when a vehicle squeezes into a line of other vehicles. According to this method, when a first vehicle squeezes in front of a second vehicle in a line of vehicles, the second vehicle and the subsequent vehicles in the line reduce their speed, starting with the rearmost vehicle up to the second vehicle. In more detail, each of the vehicles between the second vehicle and the rearmost vehicle of the line regulates its driving speed so as to keep a predetermined distance to the vehicle behind while exchanging driving information by vehicle-to-vehicle communication.
Another typical traffic difficulty is seen in two vehicles that cannot pass by each other in a narrow road. This difficult situation occurs because a vehicle does not have any means for being informed of another vehicle coming from the far side of the narrow road or currently driving on the narrow road. This deadlock could be avoided if vehicle-to-vehicle communication were available.
Sometimes, a vehicle gets stuck in an intersection, thus blocking the traffic of other vehicles in the orthogonal road. This is caused by misjudgment of the driver, who enters the intersection expecting to pass through while the signal is green, but fails to get out of the intersection before the signal turns red due to heavy traffic. The driver could get out of the intersection if vehicle-to-vehicle communication were available to ask vehicles ahead to move slightly (several tens of cm to 1 m, for example, for each vehicle) forward to reduce the inter-vehicle distances.
Vehicle-to-vehicle communication is also helpful to emergency vehicles such as ambulances and fire engines, which conventionally use a siren to notify other regular vehicles in the vicinity that an emergency vehicle is approaching. Unfortunately, regular vehicles do not notice an emergency vehicle until it comes quite close. Furthermore, regular vehicles may find it difficult to quickly clear the way if they are driving in a busy street, thus preventing the emergency vehicle from passing smoothly, and therefore, it cannot reach its destination as soon as possible. All regular vehicles may clear the way in some cases; yet the manner of clearing the way may not be the most convenient for the emergency vehicle due to lack of means for vehicle-to-vehicle communication.